Etienne88 said:
thanks for the equation
it follows that the assumption is true in practice (that is for most listening rooms) for the frequencies most important for sound localization that is above ~500 Hz
Etienne88 said:
well, all I can say is that it is also my point of view
I'm glad to hear that You gave this Beveridge speaker positioning a try and that You liked it
best,
graaf
There doesn't have to be only the two extremes - modify the room to fit the loudspeaker OR modify the loudspeaker to fit the room. The ideal is to find what combination of both yields the best result. I don't think that the optimum can be reached with only doing the room OR the loudspeaker - you must consider both and work them together as a single system to be optimized.
graaf said:
Reading Stig Carlsson document made me realise that below F2, the "reflected" waves are in phase with the direct waves (since the wavelength are big). That's also why we get a bass boost at the lower frequencies due to the room.
So there is no problem with your assumptions...
gedlee said:
I fully agree on that!
I started doing some readings (that I didn't fully digest yet...!) about the perception of reflected sound. Depending on the level of the reflected sound (relative to the direct sound, of course) and the delay of the reflected sound, the reflection can be perceived as an echo, a broadening of the image, spaciousness or not perceived at all. Echo is clearly unwanted! Image broadening can be tolerated in very small rooms. Spaciousness would be what i would be aiming for (What is your opinion about it?). Inaudible reflexion sounds like anechoic chamber to me, which is not nice!
According to my readings, and if you want to be in the spaciousness zone, the reflexions have to be lowered by 5dB if the delay is between 5 and 15 ms and by 10 dB if the delay is below 5 ms.
With good positioning and some damping, -5dB can easily be achieved. It almost seems to easy... Am I wrong somewhere?
Graaf, I have a question for you: can you see the drivers of your LS?
I ask this because a get a better tonal balance (meaning more treble) when I see the drivers, but this means that I am standing which is not very practical...
Regards,
Etienne
Etienne88 said:!
I started doing some readings (that I didn't fully digest yet...!) about the perception of reflected sound. Depending on the level of the reflected sound (relative to the direct sound, of course) and the delay of the reflected sound, the reflection can be perceived as an echo, a broadening of the image, spaciousness or not perceived at all. Echo is clearly unwanted! Image broadening can be tolerated in very small rooms. Spaciousness would be what i would be aiming for (What is your opinion about it?). Inaudible reflexion sounds like anechoic chamber to me, which is not nice!
According to my readings, and if you want to be in the spaciousness zone, the reflexions have to be lowered by 5dB if the delay is between 5 and 15 ms and by 10 dB if the delay is below 5 ms.
With good positioning and some damping, -5dB can easily be achieved. It almost seems to easy... Am I wrong somewhere?
Graaf, I have a question for you: can you see the drivers of your LS?
I ask this because a get a better tonal balance (meaning more treble) when I see the drivers, but this means that I am standing which is not very practical...
Regards,
Etienne
Reflections after 15 ms are highly desirable, especially if lateral, because they create spaciosness. Delays less than 10 ms do no good at any time. It is not easy to lower all reflections < 10 ms. by AT LEAST 5 dB (I'd say 10 dB) unless you make the room very dead, but then you kill the spaciousness. You must use high directivity speakers pointed so that they minimize the early reflections, but still excite the later reflections by using a lively room. Wide directivity speakers cannot achieve the low reflections < 10 ms without having a very dead room.
This is precisely where the speaker and room have to work together to achieve the right balance of direct to refections delay and spectral balance between the direct sound and the reverberant sound. Only a CD device of narrow directivity can do this. Nothing else works. And even with narrow directivity, you still almost always have a floor and ceiling reflection that you must do something about (because most rooms are shorter than they are wide). Vertical reflections are never a good thing, although if > 20 ms they are kind of benign especially if not from the forward direction.
gedlee said:
of course! I agree absolutely – loudspeakers and room as a single system!
well, but there is a fatal problem with this design approach of speakers with "modifying the room to fit the loudspeaker" in mind
because in practice a room is something given because apartments and houses are nor designed for "audio purposes", their design takes into account other factors and priorities and this cannot be changed
therefore IMO this design approach (that assumes "using" a room that fits the loudspeskers) leads to decline of HiFi into it's current market and social niche
the only way out of this niche is a loudspeaker that fits a normal living room while being visually unobtrusive
a loudspeaker that doesn’t need a "modified room"
"the problem with HiFi" (to borrow the name from other thread) is EXACTLY the problem of loudspeakers that need "modified rooms", "dedicated audiophile listening rooms" and such thing s like positioning 1.5 m away from room walls (that is in the middle of the room) to fulfill their promise of good sound at least to some degree
otherwise they are big disappointment especially for their price and visual obtrusion, the décor ruin they cause
no surprise that a non-audiophile does not know "what is the point of all this?"
especially as non-audiophile is naturally comparing the sound of this thing to the "real thing" as she/he doesn’t have that "audiophile brain-ear reference" (that is "comparing the sound of a HiFi gear to the sound of other HiFi gear"), only the "real thing" reference of live music and she/he has no idea that according to an audiophile "HiFi is not about" mimicking the "real thing", that "this hobby is about something entirely different" and so on
truth is that most people LOVE music and would LOVE to have at home something resembling the "real thing"
typical audiophile HiFi gear in a suboptimal setup simply fails to meet their expectations
and for most part it is the problem of loudspeaker that is like another family member that needs his/her own room and to make things worse in fact it needs a much bigger room than a "human" family member, than a second or third bedroom in a typical apartment or house
quite "a separate living room for loudspeakers"
this is absurd for most people
a second living room where You have to go to listen to the music, and to appreciate it best You have to listen alone of course because the "sweet spot" is so small with conventional loudspeakers
another absurd
but without "dedicated room" nor "head-in-the-vice" the result is nowhere near anything even resembling the "real thing"
simply "much ado about nothing" for most people
and add to this things like "audiophile cables" that are on top of all that as final proof of mental instability of "an audiophile"
no surprise that most people who are keen on music, real music lovers, record collectors and so on are typically not keen on HiFi and listen to a micro or mini systems (and I know a lot of them)
and no surprise that the term "audiophile" sounds like meaning a person with a psychological problem (like "necrophile" for example), somebody weird at best and simply disturbing at worst
I am rather reluctant to admit to newly met people that "I am an audiophile"
it is like saying "hello! I have a silly compulsive obsession!" 
I look at CD speakers like Yours as an attempt to overcome this room problem, an attempt to design speakers that are "room-proof" to some degree.
I think that their commercial failure can be partly attributed to their wrong market positioning that was fatally combined with their low WAF looks. I think that AI-Audio missed its target market and that their non-audiophile sound ("dull, lifeless... blah blah blah") could be more appreciated by non-audiophile music lovers
...if only women could accept their look
best,
graaf
Etienne88 said:
Graaf, I have a question for you: can you see the drivers of your LS?
I ask this because a get a better tonal balance (meaning more treble) when I see the drivers, but this means that I am standing which is not very practical...
yes I can see them
can You post a schematic drawing of Your current setup - how exactly the loudspeakers are positioned?
best,
graaf
gedlee said:
Only a CD device of narrow directivity can do this?
well, I don’t know
please take a look at Beveridge brochure
it seems that Beveridge line source positioned on the opposite walls can do this, in a bigger room (but not overly big) all lateral reflections can be delayed by 15 ms
moreover - in case of Beveridge line source also the floor and ceiling reflections would be no problem
of course it is only a brochure not a peer-review paper but the reasoning is convincing
any comment?
best,
graaf
graaf said:
I looked at the designs. Seems like an expensive approach that requires some very specific things to happen for the technology to be effective. It might work in some circumstances, but the "white paper" glosses over several key issues. And NO data is shown on the speakers performance itself. Thats a very suspiciuos omission.
Interesting stuff. This thread gets better - thanks for joining in, Earl. Always good to have someone who has researched and measured the issues take part.
The only system I've experienced which tries to do away with the sweet spot is Ted Jordan's small line array. It holds a remarkably stable image from left to right. The array does have the disadvantage that, when listening too close, HF drops as you stand with ears above the levle of the array. This would presumably be lessened if listening from a greater distance. His home system is designed to blend into the room as much as possible, so you are not aware of the speakers visually or as sources for the music.
Earl - I read somewhere that you prefer surround to conventional two-channel stereo. Presumbly integration problems are compounded with four or more speakers?
The only system I've experienced which tries to do away with the sweet spot is Ted Jordan's small line array. It holds a remarkably stable image from left to right. The array does have the disadvantage that, when listening too close, HF drops as you stand with ears above the levle of the array. This would presumably be lessened if listening from a greater distance. His home system is designed to blend into the room as much as possible, so you are not aware of the speakers visually or as sources for the music.
Earl - I read somewhere that you prefer surround to conventional two-channel stereo. Presumbly integration problems are compounded with four or more speakers?
Colin said:
a system that "is designed to blend into the room as much as possible" - EXACTLY! this is what is needed
Jordan recommends positioning of the loudspeakers as close to room walls as possible:
see: http://www.tnt-audio.com/intervis/jordan_e.html
BTW does anybody know Jordan's textbook "Loudspeakers" Focal Press 1962, which allegedly "has never been equalled for it's full mathematical analysis of loudspeaker theory and first principle derivation of all loudspeaker parameters, (now often referred to as the 'TS' parameters)"?
best,
graaf
Yes, I have a copy of the book. It is excellent. When I first read it, I was surprised at how little new stuff had come along since it was written (at least in terms of basic enclosures). There is some material about loudspeakers and rooms in the book but obviously it was before the availability of computer aided measuring hardware.
Ted is trying to get the book back into print. If no publisher picks up on it, we may have to try marketing it as a PDF download. Keep an eye on his website for details.
Ted is trying to get the book back into print. If no publisher picks up on it, we may have to try marketing it as a PDF download. Keep an eye on his website for details.
Colin said:
Thats not really correct. I prefer a three channel system to two, the center adds a lot, but I can do without the other suround channels. What you were probably refering to is my preference for DVD audio because its sound quality is often better. I think that this has more to do with the standardization of film audio mixing over CDs (which have no standard). CD quality has no controls of any kind, film does.
graaf said:
Have you read my book?
Aha - you have two books on your site. GM pointed me in their direction a while ago. Which do you recommend for a general grounding in the sort of subjects we're tackling in this thread?
BTW, interesting about three channel. Again, this is something Ted wrote about in the 70s, advocating its use to make a more stable centre image. He used two fullrange drivers L and R, crossing in front of the listener, and a third in the centre, pointing up (the orientation was purely to roll off HF). Not quite what we think of as surround these days but interesting nontheless.
BTW, interesting about three channel. Again, this is something Ted wrote about in the 70s, advocating its use to make a more stable centre image. He used two fullrange drivers L and R, crossing in front of the listener, and a third in the centre, pointing up (the orientation was purely to roll off HF). Not quite what we think of as surround these days but interesting nontheless.
Colin said:
Transducers book is very technical - graduate engineering level (thats why I questioned the statement above). Its the better of the two books, but it is very high level. The other book is much lower level and in fact I am rewritting it and posting the rewrites for free.
I too advocate crossing the speakers in front of the listener as this has many advantages. BUT in order to do this you must have very well controlled directivity patterns because the listener can easily be 45° off axis. Not many speakers are flat 45° off axis.
Thanks for that. I'll have a look at the second title. Do you intend republishing as a dead tree edition when the updates are complete?
Ted's drivers are all about controlled directivity, although he goes for a 30 degree pattern. The speakers are then toed in to cross well in front of the listener. This works best with his 4 inch driver (rather than a single 2"), I presume because directivity extends lower. He uses the 4-unit array to achieve a similar effect with his smaller units. (Actually the larger driver has a response designed to mimic the array, rather than the other way round.)
BTW, this is my non-technical interpretation. There is a better description on his site here and here.
Ted's drivers are all about controlled directivity, although he goes for a 30 degree pattern. The speakers are then toed in to cross well in front of the listener. This works best with his 4 inch driver (rather than a single 2"), I presume because directivity extends lower. He uses the 4-unit array to achieve a similar effect with his smaller units. (Actually the larger driver has a response designed to mimic the array, rather than the other way round.)
BTW, this is my non-technical interpretation. There is a better description on his site here and here.
Colin said:
I have no concrete plans for future books.
The sites that you list have no real data only verbiage, and I don't pay much attention to verbiage in audio anymore. Talk is cheap.
There is no way to create CD with piston sources - it is impossible. And if someone claims CD then I expect to see polars proving that because virtually ever time I hear this term used its not true.
I don't trust any statements in audio these days that are not supported with facts or measurements. I post all of the data for my systems. When I say they are CD I prove it.